A model of dark energy and dark matter (original) (raw)

Dark energy and the false vacuum

Journal of Physics A: Mathematical and Theoretical, 2007

In this talk, I will present highlights of a recent model of dark energy and dark matter in which the present universe is "trapped" in a false vacuum described by the potential of an axion-like scalar field (the acceleron) which is related to a new strong interaction gauge sector, SU (2) Z , characterized by a scale Λ Z ∼ 3 × 10 −3 eV. This false vacuum model mimicks the ΛCDM scenario. In addition, there are several additional implications such as a new mechanism for leptogenesis coming from the decay of a "messenger" scalar field, as well as a new model of "low-scale" inflation whose inflaton is the "radial" partner of the acceleron.

WIMP and SIMP Dark Matter from the Spontaneous Breaking of a Global Group

We propose and study a scalar extension of the Standard Model which respects a Z 3 symmetry remnant of the spontaneous breaking of a global U (1) DM symmetry. Consequently, this model has a natural dark matter candidate and a Goldstone boson in the physical spectrum. In addition, the Higgs boson properties are changed with respect to the Standard Model due to the mixing with a new particle. We explore regions in the parameter space taking into account bounds from the measured Higgs properties, dark matter direct detection as well as measurements of the effective number of neutrino species before recombination. The dark matter relic density is determined by three classes of processes: the usual self-annihilation, semi-annihilation and purely dark matter 3 → 2 processes. The latter has been subject of recent interest leading to the so-called 'Strongly Interacting Massive Particle' (SIMP) scenario. We show under which conditions our model can lead to a concrete realization of such scenario and study the possibility that the dark matter self-interactions could address the small scale structure problems. In particular, we find that in order for the SIMP scenario to work, the dark matter mass must be in the range 7 − 115 MeV, with the global symmetry energy breaking scale in the TeV range. Contents 1 Introduction 1 2 Z 3 Dark Matter from the Breaking of a Global U (1) DM 3 2.1 Description of the Model 3 2.2 Dark Matter Relic Abundance 4 3 Constraints on the Model 6 3.1 Effective Number of Neutrino Species 6 3.2 Higgs Sector 7 3.3 Dark Matter Direct Detection 9 4 Weakly Interacting Dark Matter 9 4.1 Self-annihilating Scenario 9 4.2 Semi-annihilating Scenario 11 5 Strongly Interacting Dark Matter 13 5.1 Dark Matter Self-interactions 13 5.2 3 → 2 Dark Matter Scenario 15 5.3 The 3 → 2 Freeze-out Approximation 18 5.4 Self-interactions and the 3 → 2 Mechanism 19 6 Conclusions 20 A The Boltzmann Equation 23 B The Non-relativistic Approximation 25

Leptogenesis in a model of Dark Energy and Dark Matter

2006

A recent model of dark energy and dark matter was proposed, involving a new gauge group SU(2)ZSU(2)_ZSU(2)Z whose coupling grows strong at a scale LambdaZsim10−3eV\Lambda_Z \sim 10^{-3} eVLambdaZsim10−3eV, a result which is obtained from a simple assumption that its initial value at some high energy scale Msim1016GeVM \sim 10^{16} GeVMsim1016GeV is of the order of a typical Standard Model (SM) coupling at a similar scale. (This assumption comes naturally from an embedding of SU(2)ZSU(2)_ZSU(2)Z and the SM into a grand unified group E6E_6E6.) It is found that the proposed model contains a SM lepton-number violating Yukawa coupling involving a scalar ``messenger field'' tildebmphi(Z){\tilde{\bm{\phi}}}^{(Z)}tildebmphi(Z) (which carries both SU(2)ZSU(2)_ZSU(2)Z and electroweak quantum numbers), a SU(2)ZSU(2)_ZSU(2)Z fermion psi(Z)\psi^{(Z)}psi(Z) and a SM lepton lll. The interference between the tree-level and one-loop decay amplitude for tildebmphi(Z)topsi(Z)+l{\tilde{\bm{\phi}}}^{(Z)} \to \psi^{(Z)} + ltildebmphi(Z)topsi(Z)+l generates a SM lepton asymmetry which is subsequently converted into a baryon asymmetry through electroweak sphalero...

Exact models with non-minimal interaction between dark matter and dark energy

2008

A method for deriving Friedmann-Robertson-Walker (FRW) solutions developed in Int. J. Mod. Phys. D5(1996) [71][72][73][74][75][76][77][78][79][80][81][82][83][84], is generalized to account for models with non-minimal coupling between the dark energy and the dark matter. New quintessence and phantom (flat) FRW solutions are found. Their physical significance is discussed. Additionally, the aforementioned method is modified so that, "coincidence free" solutions can be readily derived. Besides, we review some aspects of the phantom barrier crossing. In this regard we present a model which is free from the coincidence problem and, at the same time, does the crossing of the phantom barrier ω = −1 at late time. Finally, we give additional comments on the non predictive properties of scalar field cosmological models with or without energy transfer. PACS numbers: 04.20.Jb, 04.20.Dw, 98.80.Es, 95.30.Sf, 95.35.+d

The standard model, dark matter, and dark energy: From the sublime to the ridiculous

2004

The Standard Model of cosmology of the 1980's was based on a remarkable interplay of ideas from particle theory, experiment and astrophysical observations. That model is now dead, and has been replaced by something far more bizarre. Interestingly, the aspect that has survived involves perhaps the most exotic component: dark matter that dominates the gravitational dynamics of all galaxies, and appears to be composed of a sea of new weakly interacting elementary particles. But this sea of dark matter appears to play second fiddle to an unknown energy density that appears to permeate all of space, causing the expansion of the Universe to accelerate. We are left with many more questions than answers, and our vision of the future of the Universe has completely changed.

Quintessence, Unified Dark Energy and Dark Matter, and Confinement/Deconfinement Mechanism

arXiv (Cornell University), 2018

We describe a new type of generalized gravity-matter models where f (R) = R + R 2 gravity couples in a non-conventional way to a scalar "inflaton" field, to a second scalar "darkon" field responsible for dark energy/dark matter unification, as well as to a non-standard nonlinear gauge field system containing a square-root of the ordinary Maxwell Lagrangian, which is responsible for a charge confining/deconfinfing mechanism. The essential non-conventional feature of our models is employing the formalism of non-Riemannian volume forms, i.e. metricindependent non-Riemannian volume elements on the spacetime manifold, defined in terms of auxiliary antisymmetric tensor gauge fields. Although being (almost) pure-gauge degrees of freedom, the non-Riemannian volume-forms trigger a series of important features unavailable in ordinary gravity-matter models. Upon passing to the physical Einstein frame we obtain an effective matter-gauge-field Lagrangian of quadratic "k-essence" type both w.r.t. the "inflaton" and the "darkon", with the following properties: (i) Remarkable effective "inflaton" potential possessing two infinitely large flat regions with vastly different heights ("vacuum" energy densities) describing the "early" and "late" Universe; (ii) Nontrivial effective gauge coupling constants running with the "inflaton", in particular, effective "inflaton"running coupling constant of the square-root Maxwell term, which determines the strength of the charge confienement; (iii) The confinement-strength gauge coupling constant is non-zero in the "late" Universe, i.e., charge confinement is operating, whereas it vanishes in the "early" Universe, i.e., confinement-free epoch; (iv) The unification of dark energy and dark matter is explicitly seen within the FLRW reduction, where they appear as dynamically generated effective vacuum energy density and dynamically induced dust-like matter, correspondingly.

P 2 0 1 9 ) 0 9 9 A multicomponent dark matter scenario and the experimental evidence supporting it

2019

We review a dark matter scenario with a number of favorable aspects: (1) all of the well-known successes of supersymmetry are preserved, (2) the parameters can satisfy naturalness, (3) the addition of an extended Higgs sector implies a doubly rich plethora of new particles and new physics to be discovered in the near or foreseeable future, (4) the mass of the dominant dark matter WIMP is ≤ 125 GeV/c2, (5) the gauge couplings of this particle are precisely defined, and (6) naturalness implies that its Higgs-mediated couplings are also comparable to those of a natural neutralino. Recent (and earlier) analyses of the data from Planck, Fermi-LAT, AMS-02, and other experiments indicate that (i) the positron excess at ∼ 800 GeV or above is not evidence of highmass dark matter particles (which would have disconfirmed the present theory with a rigorous upper limit of 125 GeV), (ii) the Galactic center excess of gamma rays observed by Fermi is evidence for dark matter particles with a mass b...

Further analysis of a cosmological model with quintessence and scalar dark matter

Physical Review D, 2001

We present the complete solution to a 95% scalar field cosmological model in which the dark matter is modeled by a scalar field ⌽ with the scalar potential V(⌽)ϭV 0 ͓cosh(ͱ 0 ⌽)Ϫ1͔ and the dark energy is modeled by a scalar field ⌿, endowed with the scalar potential Ṽ (⌿)ϭṼ 0 ͓sinh(␣ͱ 0 ⌿)͔ ␤. This model has only two free parameters, and the equation of state ⌿. With these potentials, the fine-tuning and cosmic coincidence problems are ameliorated for both dark matter and dark energy and the model agrees with astronomical observations. For the scalar dark matter, we clarify the meaning of a scalar Jeans length and then the model predicts a suppression of the mass power spectrum for small scales having a wave number kϾk min,⌽ , where k min,⌽ Ӎ4.5h Mpc Ϫ1 for Ӎ20.28. This last fact could help to explain the death of dwarf galaxies and the smoothness of galaxy core halos. From this, all parameters of the scalar dark matter potential are completely determined. The dark matter consists of an ultralight particle, whose mass is m ⌽ Ӎ1.1ϫ10 Ϫ23 eV and all the success of the standard cold dark matter model is recovered. This implies that a scalar field could also be a good candidate the dark matter of the Universe.

Simulations of quintessential cold dark matter: beyond the cosmological constant

Monthly Notices of the Royal Astronomical Society, 2010

We study the nonlinear growth of cosmic structure in different dark energy models, using large volume N-body simulations. We consider a range of quintessence models which feature both rapidly and slowly varying dark energy equations of state, and compare the growth of structure to that in a universe with a cosmological constant. We use a four parameter equation of state for the dark energy which accurately reproduces the quintessence dynamics over a wide range of redshifts. The adoption of a quintessence model changes the expansion history of the universe, the form of the linear theory power spectrum and can alter key observables, such as the horizon scale and the distance to last scattering. We incorporate these effects into our simulations in stages to isolate the impact of each on the growth of structure. The difference in structure formation can be explained to first order by the difference in growth factor at a given epoch; this scaling also accounts for the nonlinear growth at the 15% level. We find that quintessence models that are different from ΛCDM both today and at high redshifts (z ∼ 1000) and which feature late (z < 2), rapid transitions in the equation of state, can have identical baryonic acoustic oscillation (BAO) peak positions to those in ΛCDM. We find that these models have higher abundances of dark matter haloes at z > 0 compared to ΛCDM and so measurements of the mass function should allow us to distinguish these quintessence models from a cosmological constant. However, we find that a second class of quintessence models, whose equation of state makes an early (z > 2) rapid transition to w = −1, cannot be distinguished from ΛCDM using measurements of the mass function or the BAO, even if these models have non-negligible amounts of dark energy at early times.